A More Open Approach Is Needed to Develop Cell-Based Fish Technology: It Starts with Zebrafish

Abstract

The global demand for fish is rising and projected to increase for years to come. However, there is uncertainty whether this increased demand can be met by the conventional approaches of capture fisheries and fish farming because of wild stock depletion, natural resource requirements, and environmental impact concerns. One proposed complementary solution is to manufacture the same meat directly from fish cells, as cell-based fish. More than 30 ventures are competing to commercialize cell-based meat broadly, but the field lacks a foundation of shared scientific knowledge, which threatens to delay progress. Here, we recommend taking a research-focused, more open and collaborative approach to cell-based fish meat development that targets lean fish and an unlikely but very attractive candidate for accelerating research and development, the zebrafish. Although substantial work lies ahead, cell-based meat technology could prove to be a more efficient, less resource-intensive method of producing lean fish meat. The global demand for fish is rising and projected to increase for years to come. However, there is uncertainty whether this increased demand can be met by the conventional approaches of capture fisheries and fish farming because of wild stock depletion, natural resource requirements, and environmental impact concerns. One proposed complementary solution is to manufacture the same meat directly from fish cells, as cell-based fish. More than 30 ventures are competing to commercialize cell-based meat broadly, but the field lacks a foundation of shared scientific knowledge, which threatens to delay progress. Here, we recommend taking a research-focused, more open and collaborative approach to cell-based fish meat development that targets lean fish and an unlikely but very attractive candidate for accelerating research and development, the zebrafish. Although substantial work lies ahead, cell-based meat technology could prove to be a more efficient, less resource-intensive method of producing lean fish meat. Over the next 30 years, the global population is projected to increase from 7.7 billion to as many as 9.7 billion people, with rapid growth and urbanization in less developed parts of the world.1United Nations, Department of Economic and Social Affairs, Population DivisionWorld Population Prospects 2019: Highlights. ST/ESA/SER.A/423, 2019Google Scholar Along with more people needing food, diets in developing countries are expected to consist of more meat, including finfish,2FAOThe future of food and agriculture—trends and challenges.http://www.fao.org/3/a-i6583e.pdfDate: 2017Google Scholar which, moving forward, we refer to as “fish.” Based on these trends, we likely face an expanding demand for meat for years to come, and meeting this demand with more efficient use of resources presents a key challenge.2FAOThe future of food and agriculture—trends and challenges.http://www.fao.org/3/a-i6583e.pdfDate: 2017Google Scholar Fish and seafood—which includes fish, crustaceans, mollusks, and other aquatic animals, but excludes reptiles, seaweeds, and other aquatic plants—already supports 20% of the global demand for consumed animal protein.3Costello C. Cao L. Gelcich S. Cisneros M.A. Free C.M. Froehlich H.E. Galarza E. Golden C.D. Ishimura G. Macadam-Somer I. et al.The Future of Food from the Sea. World Resources Institute, 2019https://oceanpanel.org/sites/default/files/2019-11/19_HLP_BP1%20Paper.pdfGoogle Scholar This percentage is even higher, on average, in the Global South, ranging from 16.8% to 56.5% in low- or middle-income Asian and African countries.4Belton B. Thilsted S.H. Fisheries in transition: food and nutrition security implications for the global South.Glob. Food Secur. 2014; 3: 59-66Crossref Scopus (141) Google Scholar Among several roles that it plays in our food system, including substantial income generation, particularly in the Global South,5FAOThe state of world fisheries and aquaculture 2018—meeting the sustainable development goals. CC BY-NC-SA 3.0 IGO, Rome. License2018Google Scholar fish meat provides essential nutrition. As an animal protein, fish is a source of high-quality, easily digested protein,2FAOThe future of food and agriculture—trends and challenges.http://www.fao.org/3/a-i6583e.pdfDate: 2017Google Scholar and supplies micronutrients not found as readily in plant-derived foods such as iron, zinc, vitamin A, and vitamin B12.6Hicks C.C. Cohen P.J. Graham N.A.J. Nash K.L. Allison E.H. D’Lima C. Mills D.J. Roscher M. Thilsted S.H. Thorne-Lyman A.L. et al.Harnessing global fisheries to tackle micronutrient deficiencies.Nature. 2019; 574: 95-98Crossref PubMed Scopus (214) Google Scholar However, despite the current and growing importance of fish and seafood in food security and nutrition for billions of people, our ability to meet increased demand for fish is being called into question. Pressure on fisheries stocks through capture fisheries has increased over the past 40 years to the point that 33.1% of stocks are overfished beyond biological sustainability and some populations are in decline.5FAOThe state of world fisheries and aquaculture 2018—meeting the sustainable development goals. CC BY-NC-SA 3.0 IGO, Rome. License2018Google Scholar Although some projections propose that, with improved management and policies in place, wild fisheries could produce almost 20% more today, and nearly all (98%) depleted stocks could recover globally by 2050,7Costello C. Ovando D. Clavelle T. Strauss C.K. Hilborn R. Melnychuk M.C. Branch T.A. Gaines S.D. Szuwalski C.S. Cabral R.B. et al.Global fishery prospects under contrasting management regimes.Proc. Natl. Acad. Sci. U S A. 2016; 113: 5125-5129Crossref PubMed Scopus (356) Google Scholar other reports indicate that output from capture fisheries has stagnated and will not increase.8Ahmed N. Thompson S. Glaser M. Global aquaculture productivity, environmental sustainability, and climate change adaptability.Environ. Manage. 2019; 63: 159-172Crossref PubMed Scopus (91) Google Scholar Based on this current understanding and information, it remains unclear as to whether conventional capture fishery methods can generate additional output to help meet the growing demand for fish protein. The other primary source of fish protein is fish farming, as part of aquaculture, which has been expanding in recent decades, partially in response to dwindling wild fish stocks.5FAOThe state of world fisheries and aquaculture 2018—meeting the sustainable development goals. CC BY-NC-SA 3.0 IGO, Rome. License2018Google Scholar Aquaculture, now the fastest-growing food production system by total volume,5FAOThe state of world fisheries and aquaculture 2018—meeting the sustainable development goals. CC BY-NC-SA 3.0 IGO, Rome. License2018Google Scholar is predicted to double its output by 2050.3Costello C. Cao L. Gelcich S. Cisneros M.A. Free C.M. Froehlich H.E. Galarza E. Golden C.D. Ishimura G. Macadam-Somer I. et al.The Future of Food from the Sea. World Resources Institute, 2019https://oceanpanel.org/sites/default/files/2019-11/19_HLP_BP1%20Paper.pdfGoogle Scholar,5FAOThe state of world fisheries and aquaculture 2018—meeting the sustainable development goals. CC BY-NC-SA 3.0 IGO, Rome. License2018Google Scholar,9Gentry R.R. Froehlich H.E. Grimm D. Kareiva P. Parke M. Rust M. Gaines S.D. Halpern B.S. Mapping the global potential for marine aquaculture.Nat. Ecol. Evol. 2017; 1: 1317-1324Crossref PubMed Scopus (218) Google Scholar Although aquaculture might be able to keep pace with rising demand, there are concerns regarding its resource requirements and resulting pollution and habitat loss.10Froehlich H.E. Runge C.A. Gentry R.R. Gaines S.D. Halpern B.S. Comparative terrestrial feed and land use of an aquaculture-dominant world.Proc. Natl. Acad. Sci. U S A. 2018; 115: 5295-5300Crossref PubMed Scopus (111) Google Scholar As with all farming of meat that requires feed, fish farming is essentially a method of transforming one source of protein (that contained in feed) into another (the fish meat). In doing so, aquaculture requires tracks of arable land to grow soy and corn11Fry J.P. Mailloux N.A. Love D.C. Milli M.C. Cao L. Feed conversion efficiency in aquaculture: do we measure it correctly?.Environ. Res. Lett. 2018; 13: 024017Crossref Scopus (76) Google Scholar or the depletion of finite forage fish stocks to produce fish meal, all for feed.12Hua K. Cobcroft J.M. Cole A. Condon K. Jerry D.R. Mangott A. Praeger C. Vucko M.J. Zeng C. Zenger K. et al.The future of aquatic protein: implications for protein sources in aquaculture diets.One Earth. 2019; 1: 316-329Abstract Full Text Full Text PDF Scopus (190) Google Scholar This is an inefficient form of protein conversion, as, on a weighted average basis, the protein retention of aquaculture is 19% (ranging from 14% to 28%)11Fry J.P. Mailloux N.A. Love D.C. Milli M.C. Cao L. Feed conversion efficiency in aquaculture: do we measure it correctly?.Environ. Res. Lett. 2018; 13: 024017Crossref Scopus (76) Google Scholar (Figure S1), analogous to discarding more than 80% of the feed protein inputs during production. Although more sustainable feed input options are being pursued (e.g., insects, food wastes, and fisheries by-products), there remains a great deal of uncertainty as to whether these can be scaled to meet demand.12Hua K. Cobcroft J.M. Cole A. Condon K. Jerry D.R. Mangott A. Praeger C. Vucko M.J. Zeng C. Zenger K. et al.The future of aquatic protein: implications for protein sources in aquaculture diets.One Earth. 2019; 1: 316-329Abstract Full Text Full Text PDF Scopus (190) Google Scholar Given the concerns around output for capture fisheries and sustainability for fish farming, it seems prudent to investigate complementary solutions to help meet the rising demand for fish meat. One innovative approach that has gathered increased attention and investment of late is cell-based meat,13Dolgin E. Sizzling interest in lab-grown meat belies lack of basic research.Nature News. 2019; (February 6, 2019)https://www.nature.com/articles/d41586-019-00373-wDate: 2019Crossref Scopus (13) Google Scholar intended as a direct meat replacement, unlike plant-based meat, which is a meat alternative (Box 1). Grounded in a hypothesis articulated by Winston Churchill in 1932 that it will someday be possible to produce meat more efficiently and economically by growing it directly from animal cells,14National Churchill Museum (2019). Fifty Years Hence, 1931. https://www.nationalchurchillmuseum.org/fifty-years-hence.html.Google Scholar cell-based meat proposes to do precisely this. With current know-how in regenerative medicine, stem cell science, muscle biology, tissue bioengineering, and bioprocessing, some suggest that commercial production of cell-based meat might soon be possible.15Danley, S. (2020). Cell-based meats approaching scalability. Food Business News, January 27, 2020. https://www.foodbusinessnews.net/articles/15286-cell-based-meats-approaching-scalability.Google Scholar Proponents contend that cell-based fish and seafood might mitigate some of the sustainability issues associated with capture fisheries and aquaculture, including uncertain supply, land demands, and stock depletion.16Rubio N. Datar I. Stachura D. Kaplan D. Krueger K. Cell-based fish: a Novel approach to seafood production and an opportunity for cellular agriculture.Front. Sust. Food Syst. 2019; 3https://doi.org/10.3389/fsufs.2019.00043Crossref PubMed Scopus (26) Google Scholar To support development, cell-based meat has been backed primarily by private investors within a venture capital model, and there are more than 30 funded startups (as of early 2020) pursuing end-to-end food solutions in a system based on competition.13Dolgin E. Sizzling interest in lab-grown meat belies lack of basic research.Nature News. 2019; (February 6, 2019)https://www.nature.com/articles/d41586-019-00373-wDate: 2019Crossref Scopus (13) Google Scholar,17Fox Cabane O. https://static1.squarespace.com/static/5b9f712ff93fd4ab389d7b82/t/5e45e2c745646d18abb40458/1581638350283/NewProteinV.2.8.pngDate: 2019Google Scholar An amalgam of different factors, including an emphasis on impact, and unique intellectual property has resulted in cell-based fish ventures selecting what are commonly known as fatty species of fish, such as coho salmon and bluefin tuna,18Hirsh, S. (2019). This lab-grown salmon could help reduce overfishing and save so many fish. Green Matters. https://www.greenmatters.com/p/lab-grown-salmon-wild-type.Google Scholar,19Finless Foods (2020). https://finlessfoods.com/.Google Scholar while overlooking what are likely to be fundamentally simpler approaches. The private system has also resulted in a severe lack of transparency, to the extent that current technological progress is almost entirely unknown.13Dolgin E. Sizzling interest in lab-grown meat belies lack of basic research.Nature News. 2019; (February 6, 2019)https://www.nature.com/articles/d41586-019-00373-wDate: 2019Crossref Scopus (13) Google Scholar Therefore, a different path to cell-based meat development seems warranted.Box 1Beyond Plant-Based MeatsOne proposed solution to address the increasing demand for meat is plant-based meat, which uses plants and other non-animal ingredients to create products that look, smell, taste, and feel like animal meat. The plant-based meat industry has received media and investment attention for its measurable impact on sustainability20Schroeder B. https://www.forbes.com/sites/bernhardschroeder/2019/06/18/plant-based-food-products-started-with-milk-now-taking-on-meat-whats-next/#2126512221daDate: 2019Google Scholar and commercial successes, most notably for plant-based hamburgers (ground meat) from food technology companies Impossible Foods and Beyond Meat.21Piper K. https://www.vox.com/future-perfect/2019/5/13/18617828/impossible-foods-meatless-burgers-investorsDate: 2019Google Scholar,22Reinicke C. https://markets.businessinsider.com/news/stocks/beyond-meat-stock-price-breaks-200-per-share-2019-7-1028376980Date: 2019Google Scholar Because the production of plant-based meats does not involve the conversion of plant proteins into muscle proteins, their protein retention is high, approximately 72%.23Alexander P. Brown C. Arneth A. Dias C. Finnigan J. Moran D. Rounsevell M.D.A. Could consumption of insects, cultured meat or imitation meat reduce global agricultural land use?.Glob. Food Secur. 2017; 15: 22-32Crossref Scopus (148) Google Scholar With a growing set of products, plant-based meats (including plant-based fish products) are providing consumers with more sustainable choices. Unfortunately, the contribution of plant-based meat production to improved planetary and food sustainability, although measurable, might not actually be so pronounced when considering resource requirements for production.23Alexander P. Brown C. Arneth A. Dias C. Finnigan J. Moran D. Rounsevell M.D.A. Could consumption of insects, cultured meat or imitation meat reduce global agricultural land use?.Glob. Food Secur. 2017; 15: 22-32Crossref Scopus (148) Google Scholar,24Hilborn R. Banobi J. Hall S.J. Pucylowski T. Walsworth T.E. The environmental cost of animal source foods.Front. Ecol. Environ. 2018; 16: 329-335Crossref Scopus (111) Google Scholar Also, cultural associations with meat are difficult to change.23Alexander P. Brown C. Arneth A. Dias C. Finnigan J. Moran D. Rounsevell M.D.A. Could consumption of insects, cultured meat or imitation meat reduce global agricultural land use?.Glob. Food Secur. 2017; 15: 22-32Crossref Scopus (148) Google Scholar Moreover, the range of uses for alternative meats is limited, as they are not functionally equivalent to conventional meats.25Samard S. Ryu G.-H. A comparison of physicochemical characteristics, texture, and structure of meat analogue and meats.J. Sci. Food Agric. 2019; 99: 2708-2715Crossref PubMed Scopus (48) Google Scholar Made of multiple ingredients, plant-based meats cannot act as replacements for the single ingredient of meat in the manufacturing process of existing products. Thus, alternative proteins are generally restricted to new products, giving consumers more choices but not offsetting products that use traditional meat. One proposed solution to address the increasing demand for meat is plant-based meat, which uses plants and other non-animal ingredients to create products that look, smell, taste, and feel like animal meat. The plant-based meat industry has received media and investment attention for its measurable impact on sustainability20Schroeder B. https://www.forbes.com/sites/bernhardschroeder/2019/06/18/plant-based-food-products-started-with-milk-now-taking-on-meat-whats-next/#2126512221daDate: 2019Google Scholar and commercial successes, most notably for plant-based hamburgers (ground meat) from food technology companies Impossible Foods and Beyond Meat.21Piper K. https://www.vox.com/future-perfect/2019/5/13/18617828/impossible-foods-meatless-burgers-investorsDate: 2019Google Scholar,22Reinicke C. https://markets.businessinsider.com/news/stocks/beyond-meat-stock-price-breaks-200-per-share-2019-7-1028376980Date: 2019Google Scholar Because the production of plant-based meats does not involve the conversion of plant proteins into muscle proteins, their protein retention is high, approximately 72%.23Alexander P. Brown C. Arneth A. Dias C. Finnigan J. Moran D. Rounsevell M.D.A. Could consumption of insects, cultured meat or imitation meat reduce global agricultural land use?.Glob. Food Secur. 2017; 15: 22-32Crossref Scopus (148) Google Scholar With a growing set of products, plant-based meats (including plant-based fish products) are providing consumers with more sustainable choices. Unfortunately, the contribution of plant-based meat production to improved planetary and food sustainability, although measurable, might not actually be so pronounced when considering resource requirements for production.23Alexander P. Brown C. Arneth A. Dias C. Finnigan J. Moran D. Rounsevell M.D.A. Could consumption of insects, cultured meat or imitation meat reduce global agricultural land use?.Glob. Food Secur. 2017; 15: 22-32Crossref Scopus (148) Google Scholar,24Hilborn R. Banobi J. Hall S.J. Pucylowski T. Walsworth T.E. The environmental cost of animal source foods.Front. Ecol. Environ. 2018; 16: 329-335Crossref Scopus (111) Google Scholar Also, cultural associations with meat are difficult to change.23Alexander P. Brown C. Arneth A. Dias C. Finnigan J. Moran D. Rounsevell M.D.A. Could consumption of insects, cultured meat or imitation meat reduce global agricultural land use?.Glob. Food Secur. 2017; 15: 22-32Crossref Scopus (148) Google Scholar Moreover, the range of uses for alternative meats is limited, as they are not functionally equivalent to conventional meats.25Samard S. Ryu G.-H. A comparison of physicochemical characteristics, texture, and structure of meat analogue and meats.J. Sci. Food Agric. 2019; 99: 2708-2715Crossref PubMed Scopus (48) Google Scholar Made of multiple ingredients, plant-based meats cannot act as replacements for the single ingredient of meat in the manufacturing process of existing products. Thus, alternative proteins are generally restricted to new products, giving consumers more choices but not offsetting products that use traditional meat. In this Perspective we, a multidisciplinary team of authors, propose a simpler approach to cell-based meat development grounded in a philanthropic, more open model. We outline the case for why lean fish, a set of species with low fat content in their muscle,26Kling P. Jonsson E. Nilsen T.O. Einarsdottir I.E. Ronnestad I. Stefansson S.O. Bjornsson B.T. The role of growth hormone in growth, lipid homeostasis, energy utilization and partitioning in rainbow trout: interactions with leptin, ghrelin and insulin-like growth factor I.Gen. Comp. Endocrinol. 2012; 175: 153-162Crossref PubMed Scopus (44) Google Scholar should be a focus for cell-based meat development as a potentially more tenable first manufacturing solution. Here, we summarize findings (see Table S1) from a conceptually based investigation and a literature-based review. We start with a minimalist framework for cell-based lean fish production, cell to fork, that includes core processing requirements. This is followed by what are likely to be the benefits of selecting fish generally and then lean fish specifically, over other consumed species with respect to these production requirements. We then present a first target lean fish species, zebrafish, that is best suited to accelerate research and development, as the most understood and studied fish species in all the life sciences by far.27Schartl M. Beyond the zebrafish: diverse fish species for modeling human disease.Dis. Models Mech. 2014; 7: 181-192Crossref PubMed Scopus (124) Google Scholar, 28Ruzicka L. Howe D.G. Ramachandran S. Toro S. Van Slyke C.E. Bradford Y.M. Eagle A. Fashena D. Frazer K. Kalita P. et al.The Zebrafish Information Network: new support for non-coding genes, richer gene ontology annotations and the alliance of genome resources.Nucleic Acids Res. 2019; 47: D867-D873Crossref PubMed Scopus (73) Google Scholar, 29Joly J.S. Aquatic model organisms in neurosciences: the genome-editing revolution.in: Jaenisch R. Zhang F. Gage F. Genome Editing in Neurosciences. Springer Copyright 2017, 2017: 21-29Crossref Scopus (4) Google Scholar We conclude this Perspective with recommendations for enabling the success of the larger, non-profit, participatory effort required to establish the science for later large-scale production of cell-based lean fish. Finally, because the grand challenge of manufacturing skeletal muscle at scale is so large, multidisciplinary, and complex, this Perspective uses simple terminology and figure imagery intended to maximize accessibility while maintaining scientific integrity. We chose words and illustrations that are accurate and consistent, but differ at times from terminology for a particular field. We are proposing a conceptual framework based on some starting technology elements that exist, but in order to meet the objective of producing full skeletal muscle at a scale necessary for mass consumption, we have to base our work on what is known in the public domain and start with high-level system requirements. Here, we run through an idealized manufacturing solution to meet this need. In this solution, cell-based lean fish will be produced by creating many identical cells (step 1) that are then directed to grow into skeletal muscle (step 2). These two steps are part of “bioprocessing,” the stage during the overall manufacturing process where cells are alive. After bioprocessing, cell functioning is no longer supported. The cell-to-fork process is segmented as inputs, bioprocessing, and output (Figure 1). The primary inputs are starter cells sourced from a small tissue sample from an animal (Figure 1A) and nutritional inputs, such as sugars and lipids (Figure 1B), which support cell functioning and contain all the amino acids (the building blocks of proteins) entering the system. In bioprocessing (Figure 1C), the two steps that starter cells undergo are doubling, whereby starter cells are produced on a large scale (in high numbers), and structuring, whereby cells already created are transformed into what we call “full-tissued meat.” By “full-tissued,” we are implying cell-based meat that retains all the essential qualities, including taste and texture, of the conventional meat it aims to replace as one ingredient. We call it “meat” and not “a fillet,” as the size and shape of the skeletal muscle output from the solution has not yet been determined. For the basic requirements of the first of the two bioprocesses, doubling, starter cells are anticipated to be suspended in a liquid composed primarily of water and other nutritional inputs of non-animal origin (Figure 1B), probably sourced from plant or microbial materials or harvested from other bioprocesses.30Mattick C.S. Landis A.E. Allenby B.R. Genovese N.J. Anticipatory life cycle analysis of in vitro biomass cultivation for cultured meat production in the United States.Environ. Sci. Technol. 2015; 49: 11941-11949Crossref PubMed Scopus (139) Google Scholar Signaling molecules (e.g., growth factors and hormones) are also required. Here, starter cells are directed to replicate repeatedly in a bioreactor (Figure 1C). With each doubling, a starter cell becomes two starter cells, each able to perform identically to the original. The doubling process must maintain starter cell health and performance capability both for continued doubling and for subsequent processing steps. An effective doubling bioprocess is essential to support the very high number of starter cells that cell-based meat manufacturing will require. As a ballpark estimate, assuming a single nucleus wet muscle cell mass of ca. 3.5 × 10−12 kg/cell31Allan S.J. De Bank P.A. Ellis M.J. Bioprocess design considerations for cultured meat production with a focus on the expansion bioreactor.Front. Sust. Food Syst. 2019; 3https://doi.org/10.3389/fsufs.2019.00044Crossref PubMed Scopus (46) Google Scholar and disregarding the negligible presence of adipocytes (fat cells) in lean fish muscle, approximately 45.2 billion starter cells must be grown in the doubling bioprocess to produce a standard, daily portion (5.5 oz/155.9 g) of lean fish32U.S. Department of Health and Human Services and U.S. Department of Agriculture2015–2020 Dietary Guidelines for Americans.Eighth Edition. 2015https://health.gov/dietaryguidelines/2015/Google Scholar (see Table S2). Using these numbers, when starting from a single cell, feeding a million people a 5.5-oz (155.9-g) portion of lean fish32U.S. Department of Health and Human Services and U.S. Department of Agriculture2015–2020 Dietary Guidelines for Americans.Eighth Edition. 2015https://health.gov/dietaryguidelines/2015/Google Scholar requires at least 64 doublings to produce close to 17 quintillion starter cells, the number 17 followed by 18 zeros. To produce these numbers, bioreactors will need to be designed at the maximum scale at which an effective doubling bioprocess can be maintained. In the second bioprocess, structuring, billions of cells from the doubling bioprocess will be seeded on “scaffolding,” a set of surfaces meant to mimic the extracellular matrix in the species and skeletal muscle tissue of interest.33Chan B.P. Leong K.W. Scaffolding in tissue engineering: general approaches and tissue-specific considerations.Eur. Spine J. 2008; 17: 467-479Crossref PubMed Scopus (900) Google Scholar Among several roles, the scaffolding should offer mechanical strength, oxygen and nutrient input transport, and waste product removal,34Olivares A.L. Lacroix D. Computational methods in the modeling of scaffolds for tissue engineering.in: Geris L. Computational Modeling in Tissue Engineering. Springer Berlin Heidelberg, 2013: 107-126Google Scholar supporting the overall functioning and development of the cells.33Chan B.P. Leong K.W. Scaffolding in tissue engineering: general approaches and tissue-specific considerations.Eur. Spine J. 2008; 17: 467-479Crossref PubMed Scopus (900) Google Scholar In a process that is anticipated to require days rather than the months needed to raise farmed fish, starter cells will be directed to differentiate and fuse (forming multinucleated cells) by exposure to specific chemical cues (growth factors and hormones),35Abmayr S.M. Pavlath G.K. Myoblast fusion: lessons from flies and mice.Development. 2012; 139: 641-656Crossref PubMed Scopus (352) Google Scholar physical cues, and nutrient inputs,36Bodiou V. Moutsatsou P. Post M.J. Microcarriers for upscaling cultured meat production.Front. Nutr. 2020; 7https://doi.org/10.3389/fnut.2020.00010Crossref PubMed Scopus (53) Google Scholar and will subsequently develop into skeletal muscle tissue.37Specht E.A. Welch D.R. Rees Clayton E.M. Lagally C.D. Opportunities for applying biomedical production and manufacturing methods to the development of the clean meat industry.Biochem. Eng. J. 2018; 132: 161-168Crossref Scopus (65) Google Scholar With respect to the critical metric of high protein retention,11Fry J.P. Mailloux N.A. Love D.C. Milli M.C. Cao L. Feed conversion efficiency in aquaculture: do we measure it correctly?.Environ. Res. Lett. 2018; 13: 024017Crossref Scopus (76) Google Scholar bioprocessing is required to convert a large percentage of amino acid mass input into full-tissued lean fish meat. In this pursuit, bioprocessing is anticipated to occur in as closed a system as possible (i.e., one where waste products are minimized and at least partially reutilized to regenerate some of the inputs). With this approach, it might be possible to design doubling and structuring bioprocesses that achieve high efficiencies and outputs, and reduce associated resource use and waste production challenges. Thus, cell-based meat bioprocessing has the potential to be less resource intensive than current animal protein production systems. However, this must, ultimately, be determined later, following considerably more research, development, and design work, and after key limitations are overcome (see A Few Hurdles below). Beyond the case for developing cell-based fish meat to help meet growing demand, targeting fish offers engineering advantages over other mammalian and avian cell-based meat approaches. For the doubling bioprocess, whereby bioreactors are used to deliver very high numbers of starter cells, the research literature indicates that fish cells are more advantageous in a number of ways.16Rubio N. Datar I. Stachura D. Kaplan D. Krueger K. Cell-based fish: a Novel approach to seafood production and an opportunity for cellular agriculture.Front. Sust. Food Syst. 2019; 3https://do